The intimate relationship of sensory and autonomic nerves with the odontoblasts is well known. Whether these nerves function to maintain, increase or decrease the activity of the odontoblast in response to external stimulation is still equivocal. Therefore it is the aim of this study to quantitatively determine if there are concomitant changes in the activity of the odontoblasts and associated nerve terminals. It is also the aim of this study to determine if newly differentiated odontoblasts, after pulp exposures, respond similarly; if the associated nerves form the same relationships to the replacement odontoblasts; and, if there are concomitant changes in the nerves relative to odonoblast activity after cavity preparation and restoration. Fifty-four, 30 day old rats will be used. Three rats will have 3H-uridine or 3H- proline injected at 15, 30 or 60 minutes following cavity preparation and restoration in the 1st maxillary and mandibular molars and 1 hr. prior to sacrifice at 1, 3, 5, 7, 10 or 14 days with the 2nd molars as controls. Rats will be sacrificed by ventricular perfusion and the tissue post fixed in 1% lanthanum hydroxide or 3% KMn04. Selected grids will be prepared for autoradiography. Another 54 rats will have the pulp exposed, pulp capped with calcium hydroxide and restored. Twenty-one days later, the restorative material will be removed and the cavity preparation reinstrumented and restored using the same methods and time periods as above. Odontoblast analysis will include quantifying uptake and incorporation of labeled precursors, location of labeling over intracellular organelles, RER and Golgi apparatus and number and distribution of mitochondria and distribution of tight and gap junctional complexes. Analysis of nerve terminals will include the type and number of vesicles present, number of mitochondria, changes in the size, length or configuration of the terminals and changes in the relationship of the terminals with the odontoblast. Information from each of the aims will be statistically compared to determine if changes in the activity of the odontoblasts are related to changes in the associated nerve terminals innervating the dental pulp.